There is indeed a fixed path in settings, but it doesn’t have the same problem of relying on an Xcode install path. Instead, GHC requires the command line developer tools package, now a separate installation which doesn’t have the option of a custom path.

(The approach of using xcode-select --print-path is still valid, and produces /Applications/Xcode.app/Contents/Developer by default under the new regime, but there’s no clear advantage to doing that any longer.)